Prior methods and apparatus for wide field fluorescence imaging can be less than ideal in at least some respects, and the prior methods and apparatus can be less than ideal in one or more of many ways. The sensitivity and specificity for diagnosis of diseases of prior wide field fluorescence imaging apparatus can be less than ideal, for example. Also, quantification of the amounts of fluorescence can be less than ideal. Wide field imaging with a small device such as an endoscope can include imaging tissue structures of objects at varying distances from the object. The varying distance can lead to variability in the intensity of the measured fluorescence. Prior methods and apparatus that may be suited for use with imaging devices such as microscopes, which may be limited to a plane, can be less than ideally suited for use with wide field imaging in which the distance of the object can vary (e.g. within a cylindrical shaped body lumen), and field-of-view is limited in real time. Also, the stability and repeatability of the measurement scans of the prior methods and apparatus can be less than ideal in at least some instances.
Determining the location and registration of prior fluorescence signals can be less than ideal in at least some instances. For example, the fluorescence measurement may be combined with one or more imaging modalities, and the fluorescence measurement itself may not provide sufficient structure to register the fluorescence signal with images from other signals.
Prior methods and apparatus of wide field fluorescence imaging can be less than ideal suited to determine subtle variations of the desired measurement signal. For example, prior methods and apparatus can be less than ideally suited to correct spectral overlap, in which a spectrum from one molecular labeling species overlaps with one or more other molecular labeling species. Also, the prior methods and apparatus can be less than ideally suited to correct background fluorescence, which can at least partially obscure a desired measurement signal in at least some instances.
The prior methods and apparatus of wide field fluorescence imaging can be less than ideally suited to measure changes over time. Measuring changes of a tissue structure over time could potentially allow the detection of subtle changes, which could lead to more accurate diagnosis and treatment. However, the prior methods and apparatus are less than ideally suited to repeatedly locate, identify, and measure changes in tissue over time for a specified location for an individual patient.
In light of the above, improved methods and apparatus for wide field spectral imaging are needed. Ideally, such improved methods and apparatus would provide one or more of the following: decreased effects of interfering background fluorescence, compensation for spectral cross-talk between fluorescent molecular labels, improved quantification of the fluorescence signal of interest, decreased quantitative errors associated with imaging distance and angle, improved co-registration of reflectance and fluorescence signals, or improved repeat measurements separated by sufficient time for tissue to change, and combinations thereof.